Static IP Address assignment vs DHCP address assignment
Solution 1:
Why were you criticised for doing it that way? I mean I think it's crazy not to use DHCP for workstations at least, but maybe there is something specific to the environment that changes that equation.
The only issue I can see with DHCP is ensuring that your scope is properly created and doesn't cross over with the pool of static addresses you use (even that can be got around with reservations but its more work than needed).
That aside, users should never ever need to know whether or not you use DHCP because their workstation should 'just work', except for when the DHCP server is not available (and if that's an issue, you just have more than one DHCP server online).
EDIT: Convict makes a good point about documentation, make sure you do have the IP address ranges documented, explaining what you've done, why and how to find it. I don't think people are comfortable with the idea that some tools are "self documenting" (and to an extent they might have a point, how would you easily re-create your DHCP database with all your reservations, if you couldn't restore from backup?).
Solution 2:
Yes, I think you're on the right track.
I suspect that you're being criticised because ...
of the lack of documentation about your network, rather than your choice of technology to assign an IP address;
you're doing IP address assignment differently to the way it's always been done. You're challenging the status quo.
Ask more questions to find out the real reason for the criticism. You may have to teach your detractors about DHCP and its benefits to your network administration.
People will come around to your way of configuring the network once they see how much easier it is to add another workstation to the network when the IP address is allocated by DHCP. DHCP should mean the end of those pesky duplicate IP address allocation errors that have plagued your network in the past.
Solution 3:
When you say the previous administrators "manually set DHCP address" do you mean static assignments?
If so, this is generally the easier way to manage pools of workstations on a LAN. Statically tie each machine's MAC address to a specific IP and deliver them by DHCP. You get the trade off of knowing exactly where each machine is and being able to change the assignments without visiting each discrete machine.
Solution 4:
Adding my vote to DHCP all the way. I can't understand why someone would criticise you for suggesting this, the whole point is to make it easier to manage the address scope, and as soon as you have more than 5 or so workstations, it makes sense.
Solution 5:
About the critics: there are still people around, that don't know DHCP with StaticIP via the MAC-Adress. They think, that DHCP = CHAOS, so you better tell em whats really in the bag.
I also can recommend different IP-ranges, something like this:
1-9 important Servers (static)
10-99 misc. Servers (static)
100-150 Sales & Marketing (DHCP with MAC)
151-200 Developers (DHCP with MAC)
200-253 Tech.Stuff (DHCP with MAC)
Another vote for DHCP is, that you can handle all IPs from one, central instance.