I am using Ownuser battery grip for my 1000D, so far no problem. There have been quite a number of reviews for third party battery grips such as Phottix and Ownuser... all of them are quite favourable. I find them okay and cheap.
For Nikon Version. I don't think so. I'm using it also. But anyway.. personal preference ba. I will not shoot during raining days so it does not affect me. E most DIY it. lolx.. put the white tape rubber around the contact point below if need it. :bsmilie:
well.. first or foremost, it depends on your luck. second depending on when and what kind of condition you will be using in. E.g. Hot day, rainy day or snowing etc.
What is your budget? Personally if you are on budget then 3rd party but some of them are just $30 to $50 difference between 3rd party and original thus in this case i will rather go for the original.
Next taking into consideration, how comfortable are you with using 3rd party product. if you wan to use 3rd party there is some risk you are taking and dun blame anybody if anything were to happen.
Above are just something for you to think about ^^