most are ok, but it always pays to have some Tamya modelling putty or such like on hand

John

The biggest problem I find with plastic kits are some of the latger panels will be warped slightly. This makes it a pain to build.

Some brands of kit are much better than others. Tamiya for example are great - all the parts fit together. Same goes with Parkside Dundas in the railway world. But some kits appear to have been designed by people who didn't realise that they were supposed to fit together.

The sad part is that so many people respond with phrases like "Proper modellers will cope". Why should they have to? A well-designed kit is a pleasure for anyone to build and produces a better result. I'd far rather spend my time on adding extra detailing than on making the basic structure fit together in the right shape.

There's a huge variability in kits and brands. Some fit better than others but really they're just models anyway. And they're just plastic so we can't expect perfection. However, when finished, they do look a little like their prototypes. That's the main thing. Actually I find the detail in most kits to be very good. It's a lot better than building from scratch out of wood like we use to. Now those were the days when models looked really junky.

Bob

I have built lots of plastic building kits, mostly Faller, and in the majority of cases the parts have been accurate and fit well together.

When parts are warped, the best solution is usually to hold everything together with elastic bands while the glue sets. Occasionally, you will need some filler to make good an imperfect joint, but in almost every case I can blame myself for having misaligned the parts.

I find it helps if you try to build the main walls with "blu-tack" or similar to check the fit before trying the same with glue.

My own experience and opinion is that especially Vollmer kits use a more rigid plastic, and parts are thinner/finer.
Add to that that their plastic also seems less tolerant to UV rays.
Almost every Vollmer model I have assembled, has caused me grief either during building or later when finished (or both ;-)
They seem to have the best desingers/most detailed kits though!

I prefer (older) Kibri kits; Thick soft plastic. Nice designs, easy to modify.

It's impossible to generalize with Faller. Their products are all over the place, quality-wise speaking. (Former Pola products seems to me more consistent in quality, and they're not too bad ;-)

Worst fitting I've seen is from Heljan. Märklin used to have several kits produced by Heljan. There are pieces which are really physically impossible to join, although the instructions states so...

I've never used any filler. I usually cut and meassure several times until the parts fit. -Also if it means cutting away extensive parts.
By using rubber-bands and adhesive tape, you can normally force warped parts together, but the result can warp the WHOLE structure.