I considered the E51 as an upgrade and although finally choosing another phone, this is a really cool phone. The reviews were all in it's favour and everyone generally likes it...
I have been using an e51 for a few months now and I love it. It feels very "snappy" and stable compared to my e65. I had to buy it unlocked (not on contract) and I got it for about R2500. Fantastic value for money, if you ask me. Highly recommended. By the way, for all you Nokia e series owners out there, here's a great site: http://www.e-series.org/