Hi
I would regard -438 as pretty good. There are no bugs in it which will make you cry. One or two small glitches here and there but we have it in production at quite a few sites.
As to hardware endorsement. As a rule we try to remain unbiased, however, we are Snom, Aastra, Multitech, Cisco/Linksys and Digium resellers so I guess we must have some bias.
For professional use we don't recommend grandstream. In most respects the GXP2000 is a pretty good low-budget phone but it has a few flaws; the speakers are awful and the non-POE power supply take-off (on the rear of the phone) is very flimsy and tends to shear away from the main housing if the unit gets dropped. For SOHO use it's probably fine and we do have a couple here which we use for testing and provisioning purposes. If you like what it does then I would recommend you take a look at the Aastra 9133i before you decide.
For professional use we tend to recommend Snoms, simply because they are the "benchmark" SIP device and they can do a lot of stuff in their own right which adds to the overall value which the customer experiences.
The Aastra range is good value for money and, being built by a trad. phone company, the acoustics are excellent. They are only let down by the the amount of bleedback which they put onto the earpiece during a call. Some customers hate this, others don't seem to mind.
Of the phones we don't sell, my personal favorite is the Polycomm. Superb build quality (if rather quirky looks) and really nice usability with the softscreen leading you through the available choices at any given time. Nice but expensive -

Digium TDM boards. We almost gave up on TDM boards earlier this year, simply because we could not crack the echo problems we were getting with them. However, since the arrival of FXOTUNE and our implementation of it into SAIL, we now get near perfect sound quality every time.
Preferred set up. We normally recommend ISDN BRI or PRI to our customers (you might be surprised at how many commercial SAIL installs NEVER make an external SIP or IAX call

).
For up to 3xBRI circuits we standardised on Billion passive cards some time ago because they just work and with the Florz patch fitted use very little CPU. For PRI we standardise on the MultiTech MVP3010 because it's a carrier class gateway and it just works.
Hope this helps
S