Haven't tried Gradius Rebirth yet, but I just downloaded Contra Rebirth this past weekend and I really like it. Not the best Contra, but certainly a very very nice surprise.
Speaking of Wiiware, it really surprised me to see several games on there that I didn't even know were out yet. At least in Europe.
I usually keep up with this kind of thing, but I've missed several weeks of updates, so I was very pleasantly surprised to see Arkanoid Plus, Bit Trip Core and Contra Rebirth on there.
After the surprise of Puzzle Bobble and the recently released and btw excellent Puzzle Bobble galaxy, this has been a great week for retro style games!