Jan 31st 2010 4:36AM I've used Healbot and when that started to break down (think it was during BC or when WotLK came) I went over to Grid+Clique. When I found Vuhdo (in its early days, around version 1.10, now it's 1.236) I really liked it. It was a bit unstable at that time so I kept grid around for a month or two which saved me a few times.
Anyway, I can fully understand those that prefer grid over it, they layout of grid is very nice. You can't really get vuhdo close enough to work like that. What I do love about it is that it's so feature rich (can be a big problem for those that don't have time/interest enough to learn enough of them). Vuhdo can really do everything you need as a healer. Debuff/buff tracking, range, status, targeting, mana and/or resource bar (you can of course have it active even if many don't feel a need for it. Incomming heals from others (work with most other healing addons also using libhealcom). Very good HoT tracking for both you and other healers in group. If you need it you can most likely count on it being there.
One feature I haven't seen mentioned here is the ability to group players in group/raid according to different criterias. The one I use is group by role. Tank, Melee, Ranged and healers (I'm pally so I have no party based heals so no need for that). It's based on talent inspection and seldomly fails. If it does you can always force it (get the vuhdo menu and select the role you know the player has). You can also add extra panels to display tanks and pets and so on depending on what you need.
Vehicle handling is also very nice, that took a while to start working, but these days the switch between players in vehicles and when they jump of work perfectly.
Some has wondered about performance. One thing about Iza is that he raids a lot and he is a very professional software developer. His focus has always been to make a feature rich but still very high performance addon. He puts much effort to optimze the code to avoid it being a problem in raids.
As mentioned, Iza is extremly active in the plusheal forum. Since march 09 there has been over 2000 entries in the vuhdo thread and it would not surprise me if Iza stands for 40-50% of those. Even if many questions has been asked 20 times he is still very polite and answers them clearly and he is also very quick to respond to any problems that show up. Some times he is a bit too quick on releasing a new version that might break something, but within a day a fixed version is out so keep it updated :-).
If you really feel good with your current setup, don't switch. If you feel that you should be able to do better try it out!