I rate the Montane Featherlite - an excellent windproof/water repellant packable jacket. I don't have one myself but the misses does and I have borrowed it. Personally, I wouldn't get the 'Velo' version because it has a full zip and the other one (is it the smock?) has 1/3 length zip. It's a preference thing but I also reckon zips are a weak point - if water/cold is going to get through anywhere it'd be the zip.
I have a similar jacket, a Rab one. It's pretty much the same as the Montane (but without a stuff sack thing) and works just as well. Both the Montane and the Rab are made of pertex - that's the stuff you want to look for.
Gilets; excellent but not really my thing to be honest. I'll go out wearing one but I've never packed one as an extra 'just in case' layer. If I want something 'just in case', I take something with sleeves - be it my Rab or my CycleChat windproof (which, I must add, is excellent).
But don't let me put you off a gilet. It is worthwhile garment, if you can afford gilet and long sleeve then do it. They'll both get used. If only the one item, then I'd go long sleeve.