HP-UX

Well I never did anything else and the only server that was migrated (10.20 -> 11.00) always gave me trouble...

What makes you think its difficult?
Why am I asking you if you are on mirrored disk, is that you can split install on the alternate and if in trouble come back by booting on the (ex)primary again...
A fresh install is by far the cleanest and is preferable unless you have applications /software that coulndt be reinstalled...

The performance gain should make it a worthwhile upgrade

If you are willing to end up with 11iv3 then forget upgrading, go for a fresh install...
You avoid 2 upgrades where you may fall on an issue that may force you to do a cold install afterall...
Good luck!

(Truly, its less pain than an upgrade... and MUCH faster: No all the prerequisites to check and applications compatiblities no link messing about etc...
I remember now I did one ( a 9.4 ->10.20 and had to pass by 10.01...) I promised I would never do that again unless I have no other choice...)

According to me, its better that you go with a "split install on the alternate" if you have a mirror as that confirms that there is no big trouble in future. If you have any issues, you can just bring back with the original disk.

It would appear easy on books to migrate, however, there are a lot which are not possible practically.. May be yes, Possible but, hard while going through.

Even if in case you do not have a mirror, its recommended that you mirror a copy first and do anything with the second copy. If in case you have a ignite, PLEASE do take a backup and do anything you prefer so anytime you have a backup to restore to the original point.

Cold install, hmmm, yes for sure since its not a hectic process, time consuming, if all your software's, applications and all are supported and you are sure, YES, you can proceed then.

Either ways, all the best man!

-DB