I'm using it and don't think it's tacky... if you put stuff on from the Zola list, you get sent the actual item, and not cash. If you add items from other sites (e.g. Amazon), it looks pretty, it's cheaper than Macy's, and you can integrate things from a million places onto one registry instead of having people visit 4 links. In addition, you can do a honeymoon registry AND a small house registry in the same place. I'm getting married across the country so people can't bring us physical gifts anyway (I mean, not ideally - I'm sure someone will!), so this makes a lot of sense for us. I've also noted on each item where it's available in person in case people prefer that.
If there were a better aggregated system that didn't use cash, I'd go for that, though. I just haven't been able to find one I liked!
Re: ZOLA wedding registry