I also install PATCHMEM and will sometimes add 512MB or more memory, but it's hard to find a good use case where more than 256MB actually makes a difference.
If you are still using Windows 98 as a power user and doing serious multitasking for anything other than nostalgia, then you're doing it wrong. No matter how stable it seems at any given time, one rogue application can tank the whole system and whatever "work" you had open at the time.
I'm a huge fan of DOS, 3.1, and 9x, but I remember when Windows 2000 was released as the first NT for the masses, and it was a godsend for anyone who needed to get some actual work done and play games on the same computer. Yes, there was always NT4, but it had very poor support for DirectX and many games from its time won't run on it at all.