I use SEOpressor only to check how good my articles rank in % for a certain keyword (how well they are optimized). I wouldn't know why it would be bad, even on a slower server?seo pressor is not good for cheap hosting and poorly managed sql DB's, just keep that in mind. You could use clickbump or easy wp seo.
Personally I spent a week testing all 3 out for functionality and server stress and found easy wp seo to be the best for that. Now the next month will be a test of the 3 different plugins in effectiveness... a much harder test to set up believe me!