It's hard to comment on overall quality of 5.1, though I have yet to hit any bugs personally after using it intermittently for almost a year. However, we have done a lot of work with MySQL row replication. Monty points out several bugs in the row replication implementation. Frankly, they would not hold me back. Row replication has so many advantages in eliminating strange corner cases from statement replication that it outweighs a few bugs. The MySQL 5.1 manual sums it up accurately:
Beyond issues like provable correctness, row replication is simply more flexible than statement replication. Heterogeneous replication is an obvious example. Our own Tungsten Replicator can replicate statements from MySQL 5.0 to Oracle. That's great if you use completely vanilla SQL and stick to int and varchar datatypes. For real applications, however, you need a data structure that transfers datatypes accurate and is easy to morph across schema differences. Similar reasoning applies when using replication for application upgrades. Finally, row replication is the only viable path for implementing parallel slave update, which is increasingly necessary on multi-core hosts. I can't speak directly for Mats Kindahl and other members of the replication team, but there's no doubt they see row replication as the foundation to solve a number of key problems.
Advantages of row-based replication:
- All changes can be replicated. This is the safest form of replication.
For these and other reasons our team at Continuent has devoted quite a bit of effort to reading row updates in MySQL 5.1 binlogs. Obviously, we have some uses in mind that go well beyond simple MySQL to MySQL data transfer. However, I would not shy away from MySQL 5.1 if I were using native replication. Instead, I would be testing row replication today to see what problems it solves for me. Congratulations to the MySQL team for getting this feature out the door.