When 10.5.0 Leopard came out an replaced 10.4.x Tiger, it was quite buggy until around 10.5.3. Aside from Snow Leopard which was a special case, new OS X releases are typically buggy for the first few months.
Vista was a dog because it was slow, resource intensive, and Microsoft never issued any updates to fix it.
The only thing I thought was a bad idea in Lion was Time Machine snapshotting your local HD every hour, to itself, when your backup drive isn't available (like on a laptop). That would kill I/O whenever it ran, slowing everything. Shutting that off fixed 90% of the problems I had.
Vista was a dog because it was slow, resource intensive, and Microsoft never issued any updates to fix it.
The only thing I thought was a bad idea in Lion was Time Machine snapshotting your local HD every hour, to itself, when your backup drive isn't available (like on a laptop). That would kill I/O whenever it ran, slowing everything. Shutting that off fixed 90% of the problems I had.