First impressions

Fine detailed mouldings, crisp and clean. Very little flash, no sink marks. Fine scribed lines that are out of scale for 1/144 but will still look good under a coat of paint. Panel lines match up very nicely. Once you get past the first look, there are two mistakes that slightly spoil the kit, but neither of them is a deal-breaker. Kids building their first airliner won't care about either of them and the rest of us can easily correct them.

Fuselage
The fuselage is two halves from nose to tail. The cabin windows are open, with no clear parts provided for them. Either fill them or Krystal clear/Clearfix them; decal film just won't do it. No interior detail is provided, and the small windows would render any interior redundant anyway. The cockpit windows are a Heller-style cockpit cap, making installation a breeze. This style is fr superior to the strip type windows. If the windows are left open, the interior should be painted black to prevent the model from looking toy-like. Revell calls for a 20g nose weight to be installed before closing the fuselage. There are no bulkheads to keep the weight from rattling around so it needs to be firmly glued down. The upper and lower VHF antennae are moulded with the left fuselage half. This means that one or more of them will have the opportunity to break off during construction and sanding.

Wings
The lower wings are one piece from tip to tip while the upper wings are in left and right halves. The trailing edge is included on the upper wing halves. The trailing edge is reasonably thin, but the modeller may decide to thin it further. The choice of winglets or plain tips is offered, but the modeller must be cautioned that Revell did not get the shape of the winglets at all correct. They're far too wide at the tips and not tall enough. Proper winglets may be robbed from a Daco/Skyline 737, or purchased from either Contrails or Bra.Z models or corrected as detailed in this Britmodeller article. (Edit: Aug 26, 2012) I am reliably infomred that the 737 "classic" winglets as provided in the Daco kit are shorter than the NG winglets. The photo shows the white kit winglets compared to a pair of grey Daco winglets. Although they are too short their shape is correct, and illustrates where Revell went wrong. Alternatively you could find a colour scheme for an aircraft that doesn't have winglets and use the plain wingtips instead. The fit of the centre section to the fuselage is a little tricky and if you're not careful you'll end up with a step. Take your time with dry-fitting and sanding until the fit improves. Tabs made of scrap plastic will help to adjust the fit on the lower fuselage fore and aft of the wings.

Empennage
The tail-planes are one piece mouldings that fit so nicely that they don't really need glue. Leave them off until final assembly to facilitate decalling.

Engines
The engines are where Revell made their second mistake with this kit. Out of the box, they're perfect for the 737-300/400/500 series but not for the -800. The Next Generation 737s (including the -600, -700, -800 and -900) have taller landing gear which allowed Boeing to redesign the nacelles to have a more nearly circular intake and deeper cowlings. The engines will have to be modified or replaced with aftermarket items available from Contrail. A pair of Contrail engines is shown, plus an engine beside the incorrect Revell intake ring showing the difference in shapes. Out of the box, the engines fit together very well and attach to their mountings without difficulty.

The Contrails engines are offered in two parts to facilitate painting and to allow for fan detail to be portrayed at either end of the cold section nacelle. (Earlier versions were made in one piece). The mating surfaces will need to be carefully cleaned up and glued with either epoxy or cyanoacrylate glues.Once assembled they are a direct replacement for the Revell engines with no modification to the kit needed.

Landing gear
The landing gear struts and wheels are finely moulded and nicely detailed. They could use some brake lines and whatever else the modeller likes, but will look good without. There is an option for raised gear, but no stand is provided. The nosewheel doors are moulded shut and must be cut apart for a gear-down model. As with all 1/144 kits, the gear doors are overly thick and may be replaced if the modeller wishes.

Accuracy
I don't compare models to drawings or published measurements. When assembled it looks like a proper 737, assuming the engines and winglets have been replaced.

Decals and markings
The decal sheets are very complete, with lots of stencils and multiple choices. Revell's decals have lately been drawn by Danny Coremans of Daco Products. You get the level of detail commonly found in his aftermarket sheets right in the box. This kit has been released several times over the years, each time with different airline choices provided for.
If you don't like the kit decals there are many different choices provided by the aftermarket industry.

Conclusion
This kit is a good one to practise conversions. It may be shortened or lengthened to portray any one of the 737 Next Generation family by simply removing or adding constant-diameter sections of the fuselage fore and aft of the wings. Detailed instructions to do any of the 4 versions are available for download from the Draw Decals website (incidentally, Draw Decals offers many different decal sheets for all versions of the 737). If cutting up a fuselage is too ambitious, Contrails offers solid resin "drop fit" fuselages for the -700 and -900 versions.