The Airfix '109F in 1/48th was considered 'the business' when first released, Daniel. Even now, it's still a pretty good kit, although the windscreen has the external armour, so needs modifying if doing a 'standard' bird. Also, the canopy is one piece, but the overall quality of the mouldings are quite good, and IIRC, the tropical filter is an optional part in the kit.
However, with the likes of ICM, Hasegawa etc at a similar price, or not that much more, it would probably be better to go with theirs. But of course, if you just want to do, for example, three '109F's in different schemes, then there's not much wrong with the Airfix kit. I'm actually going to use one for a diorama, where the aircraft will only be part of the scene, with closed canopy. The main scene will be the surroundings and small hangar. If I was going to portray the aircraft being serviced say, then I'd use a different kit, with separate flaps, canopy etc.
Basically, the original Airfix 1/48th scale range was very good when released in the late 1970's to early 1980's, at a time when this scale was only really starting to become popular. Since then, production methods have come a long way, and as a result, some older kits are considered to be second-rate, compared to the fine detail of the current offerings. But the older stuff, in many cases, is still worthwhile, especially as they tend to be a lower price, and lots can be done with them.