I've done a few manual steering rack conversions in my days, and am currently running a de-powered-but-otherwise-stock rack in my 2000 Boxster S.
I know this sounds counter-intuitive, but daily driving a de-powered rack is fine while tracking / racing a de-powered rack sucks.
Parking lot maneuvers is where a steering rack experiences the highest loads. The 986 has actually been the EASIEST of all the manual converted cars to maneuver in parking lots. At highways speeds, there is no difference in steering efforts...
...assuming you want to go straight!
Once you start trying to hold a corner at speed, this is where a manual steering rack really starts to suck.
A power steering system not only helps move the rack, it helps HOLD the rack when things like cornering loads are trying to push the wheels back straight again. That effort which was required to turn the steering wheel in the parking lot, will be similar to the effort required to hold a long sweeper at 80 - 90 mph. It's very easy to lose grip of the steering wheel and have the car pull itself centered into a code-brown moment. Ask me how I know this...
One other item to consider when de-powering the rack is that the pinion gear is intentionally built with a ~10° slop or hysteresis angle. This slop is actually what controls the assist. In a traditional hydraulic system, this slop controls a hydraulic valving to the rack. In electric systems, this slop tells the ECU how much current the assist motor needs to apply.
I strongly recommend that anyone doing a full manual swap should remove the pinion shaft from the rack and weld the two inter-locking pinion shafts (this is what give you the ~10° slop used for valving) together. Be careful though, once you go this route, there's no going back to a stock setup.
If you still want to run power steering, but hate the idea of running any hydraulics, there is also the possibility of swapping in an electric column assist. This is surprisingly the cheapest and lightest method for adding alternative power steering, but it is also SUPER labor intensive and it WILL require fabrication. This was my first application of such a system that I installed in a budget endurance race car.
Electric Powered Steering - Column Assist / NO HYDRAULICS! - Turbo Dodge Forums : Turbo Dodge Forum for Turbo Mopars, Shelbys, Dodge Daytona, Dodge SRT-4, Chrysler PT Cruiser, Omni and more!
In summary, manual steering in a Boxster would be fine for a majority of car enthusiasts. Heck, I ran all last summer with my unmodified stock rack and no steering pump. However, I'm getting old and plan on some track events this summer so I'm installing an electric hydraulic pump from a 2012 Durango with the 3.6L V6.