I'm considering upgrading to Links SQL from a Links 2.0 install that I've had for a year and a half or so. Besides the cost, I'm worried about how some things will transfer, or not transfer, to the SQL version. I know the database will transfer fine (or so I've read), so thats not my concern really. Just some mods I've added:

Username/Password protection on adding and modifying records; is this supported?
The Modify Protection mod that calls the current data after one logs in to modify their records (for example, it loads their Name in the name field instead of being empty.) This doable?
Alt-Categories?

Basically these are the ones I'm concerned about; I'd like to make the changover to SQL completely transparent to my users (for the most part), and without those, at least the first two, it would really change the way the database worked....

I'm thinking I'm going to need to upgrade soon as, eventhough my link count is only about 600, each link contains a ton of information with the links file near a meg and the category file nearing 600Kb with little slowing down so build time is getting quite high and i'm beginning to notice the bane of flat file DBs.

If these mods could be implement fine I'd just need to somehow come up with the cash lol :)